The invention relates to new compositions and methods of plant tissue culture.
Plant tissue culture is the growth, on or in artificial media, of whole plants, plants parts, organs, or undifferentiated tissue. Tissue culture has many important commercial uses such as the isolation and maintenance of virus-free strains of plants. Plant tissue culture can also be used to mass-propagate plants, and this method is used routinely in the propagation of horticultural and floral varieties for the nursery industry.
Certain difficulties detract from the benefits of tissue culture. For example, certain cultured plant tissues, in any stage of development, may be subject to vitrification (also called hyperhydricity), which results in enlarged, thick, translucent, and brittle malformations of tissue. These malformations are irreversible, and affected tissues typically degenerate and die.
Acclimation is another common problem in tissue culture. Once whole plantlets are successfully generated, they must be acclimated before being transplanted. Plants normally grow a waxy outer cuticle to prevent evaporative water loss, but the high humidity of the tissue culture environment prevents development of this protective coating. A sudden drop in humidity, such as transfer into a growth chamber or greenhouse, can kill the young plants.
A third problem is that the chemical composition of the culture medium has a large effect on all of these phenomena. Each cell, tissue source, organ type, and developmental pathway has different nutritional requirements, and these can vary greatly between species, or even between cultivars within a given specie. Determining the ideal medium for a new plant or tissue must be done through systematic trial-and-error, using knowledge of the behavior of related species as a starting point (Endress, 1994, Plant Cell Biotechnology, Springer-Verlag, Berlin, pgs. 38).